DNS tunneling: Definition & Protection

DNS tunneling is a really dangerous attack that you should be aware of. In this post today, we will take place at it: its main purpose, how it works, and how you can protect against it. So, let’s begin this adventure.

The definition of DNS tunneling

As the name implies, the DNS tunneling is a Domain Name System attack type. It uses a tunnel through which it pushes malware via the client-server model.

In fact, this attack uses DNS as a communication channel to escape the victim’s firewall. Nowadays, we all use the Internet. And to be able to use it, we allow this DNS traffic to pass through our firewall. We do this because we want to access certain sites, or if we have, to access our site. Hackers know this very well and take advantage to attack us. 

How does it work?

Let’s see how DNS tunneling works in the following steps:

  1. First, hackers obtain a domain and a server with malware running on it.
  2. Then, using a server that has been infected with malicious software, the attack cyber criminal looks for the domain. Because DNS requests are always assumed to cross and leave the firewall, the infected device can send a query to the DNS resolver.
  3. Finally, the DNS resolver creates a tunnel between the attacker and their target as it routes the query, allowing them to collect data, remotely control the server, or otherwise carry out the attack.

DNS tunneling protection

Is there a way to protect yourself from DNS tunneling attacks? Absolutely, the answer is yes! How? We’ll look at the two most common approaches.

  • The first is to put in place a firewall system. This might be the best way to protect yourself from a DNS tunneling attack. Why? Because this technology is capable of immediately detecting and stopping all unwanted traffic.
  • The second is to keep an eye on DNS traffic by implementing a DNS Monitoring system. This is yet another successful method. Why? Because you’ll be able to track DNS traffic and be notified of any potentially hazardous activity. This will help you mitigate the risks connected with DNS tunneling.

DNS tunneling and the DNS records

In order to perform this attack, DNS records must also be used. Of course, depending on the desired result, cybercriminals use different record types. But in general, they usually utilize TXT, NULL, and CNAME records. Of these, the most commonly used is the TXT record or often known as the TEXT record. Why? Because they have the largest and most diverse payload structure.


Taking everything into account, DNS tunneling is a dangerous attack that can do a lot of damage to you and your business. To prevent this from happening, take measures in advance – implement a firewall and monitoring system. Good luck!

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